1. Field of the Invention
The present invention relates to a temperature controller for a semiconductor-fabricating tool. More particularly, the present invention relates to a temperature controller for a semiconductor-fabricating tool such as a reticle box or a front opening unified pod (FOUP) that is used for fabricating a semiconductor device.
2. Description of Related Art
Semiconductor device development has increasing in importance with the widespread use of information devices such as computers. Semiconductor devices having increased operational speed and memory capacity are needed for the computers. Continued semiconductor device development needs a technology of manufacturing that has improved integration, reliability, response speed, etc. Photolithography is a technology that may be further developed for achieving improved integration of the semiconductor device.
When a semiconductor device is manufactured using a photolithography technology, a photoresist film on a wafer is exposed to form a photoresist pattern. A projection exposure apparatus may be used in the exposure process.
The projection exposure apparatus includes a light source, and a reticle on which a reticle pattern is formed. Light generated from the light source is irradiated to the reticle. The light penetrates the reticle to form a light pattern having a shape corresponding to that of the reticle pattern. The light pattern is transcribed onto the photoresist film on the wafer through a projection optical system, thereby forming the photoresist pattern.
The reticle includes a material through which the light can pass. The reticle pattern for forming the photoresist pattern is formed on the reticle. The reticle pattern may include chromium through which the light cannot pass. Slits through which the light penetrates are formed through the reticle pattern.
To prevent contamination of the reticle, a reticle box may be used for transferring the reticle to an exposure chamber. The exposure chamber is maintained at a temperature of about 22.0° C. A clean room in which the reticle box is positioned is maintained at a temperature of about 23.5° C. Thus, when the reticle is loaded into the exposure chamber from the reticle box, the reticle contracts due to a temperature difference of about 1.5° C. between the exposure chamber and the clean room. As a result, a line width between the reticle patterns is reduced so that the reticle pattern has a line width shorter than that determined in a design step. Therefore, when the exposure process is carried out using the reticle having a reduced line width, a photoresist pattern having a desired line width may not be formed.
A reticle box having a temperature controller is disclosed in Korean Patent Laid Open Publication No. 2002-0017629 and shown in FIG. 1. With reference to FIG. 1, a reticle R is received in a reticle box 1. A heating plate 2 for heating the reticle box 1 and a cooling plate 3 for cooling the reticle box 1 are disposed under the reticle box 1. Temperature sensors 4 and 5 are attached to the heating plate 2 and the cooling plate 3, respectively. A controller 6 controls operations of the heating plate 2 and the cooling plate 3 in accordance with temperatures of the heating plate 2 and the cooling plate 3 detected by the temperature sensors 4 and 5.
However, since the conventional temperature controller separately has a separate heating plate 2 and a separate cooling plate 3, the controller 6 may not accurately control the heating plate 2 and the cooling plate 3. Accordingly, since the temperature of the reticle box 1 is controlled by separate operations of the heating plate 2 and the cooling plate 3, precisely controlling the reticle box 1 may be very difficult.
FIG. 7A is a graph illustrating contracted lengths of patterns on wafers that are formed using a reticle box without a temperature controller. In FIG. 7A, the horizontal axis represents wafers, the left vertical axis represent contracted lengths of the patterns with respect to the reticle patterns in a Y-axis direction, and the right vertical axis represents contracted lengths of the patterns with respect to the reticle patterns in an X-axis direction. Line {circle around (1)} indicates transitions of the contracted lengths of the patterns in the X-axis direction, and line {circle around (2)} indicates transitions of the contracted lengths of patterns in the Y-axis direction.
As shown in FIG. 7A, a pattern on a first wafer formed using the reticle contracted by about 0.3 ppm in the positive X-axis direction. A pattern on a fourteenth wafer contracted by about 0.3 ppm in the negative X-axis direction. A pattern on a twenty-fifth wafer contracted by about 0.4 ppm in the negative X-axis direction.
The pattern on the first wafer contracted by about 2.8 ppm in the Y-axis direction. The pattern on the fourteenth wafer contracted by about 2.3 ppm in the Y-axis direction. The pattern on the twenty-fifth wafer contracted by about 2.1 ppm in the Y-axis direction.
A line width of the reticle pattern contracted beyond a designed line width when the reticle in the reticle box having a temperature of about 23.5° C. was loaded into the exposure chamber that was maintained at a temperature of about 22° C. Therefore, the pattern on the first wafer that was formed using the reticle having the contracted line width also contracted in the X-axis and Y-axis directions. As the temperature of the IS reticle was raised to that of the exposure chamber, the pattern on the twenty-fifth wafer contracted within the designed line width.
According to FIG. 7A, a desired pattern might not be formed on a wafer by an initial exposure process in which the reticle in the reticle box has a temperature different from that of the exposure chamber.
Therefore, a need exists for a temperature controller for a semiconductor-fabricating tool having improved temperature control.